1. Technical Field
The present invention relates generally to computer memory systems, and more specifically to the handling of data faults.
2. Background Art
Conventional hard disk systems implement data recovery with parity protection across multiple disks, so that data will be protected even if one disk fails. RAID (Redundant Array of Independent Disks) architectures have been developed to allow recovery from such disk failures. In a typical hard disk system, an XOR (Exclusive-OR) parity of data from a number of disks is maintained on a redundant disk. In the event of a disk failure, the data on the failed disk is reconstructed by XORing the data on the surviving disks. The reconstructed data is written to a spare disk.
A solid state drive (SSD) faces an analogous problem if the SSD comprises multiple NAND memory (or other memory) dies that all store data. In such an SSD, there is a finite probability that one such memory die will fail. With the increase in use of SSDs in a wider range of applications, there is an increasing susceptibility of computer systems to such die failures. Moreover, the rapid growth of SSD storage capacity also increases the likelihood of such computer systems encountering prolonged data recovery time in the event of die failure. For at least these reasons, the performance of SSD memory systems are increasingly sensitive to incremental improvements in efficient utilization of resources to provide for data recovery.